1. Field of the Invention
This invention relates generally to circuit breakers of the type comprising a releasable mechanism, releasable to trip the breaker and an electromechanical trip means operable to effect release of the releasable mechanism.
2. Description of the Prior Art
In the patents of Alfred E. Maier, and John A. Wafer, U.S. Pat. No. 3,783,423, issued Jan. 1, 1974 and the patent of Alfred E. Maier and Allan B. Shimp, U.S. Pat. No. 3,826,951, issued July 30, 1974, there is disclosed circuit breakers having flux transfer magnetic trip actuators of the type comprising an armature structure releasable to trip the breaker and a permanent magnetic means operating to maintain the armature structure in an initial non-tripping position. Inasmuch as the detailed description of a circuit breaker having flux transfer magnetic trip actuators is disclosed in the aforementioned patents to which reference is made for complete description of structure and operation, the description of those portions is limited to the parts that are essential to the operation of the invention disclosed herein.
Flux transfer magnetic trip actuators are designed to trip the circuit breaker when it receives a low power electronic signal from its sensing circuit that indicates an overcurrent condition in one of the three phases of the circuit breaker. The sensitivity designed into flux transfer magnetic trip actuators has made them affected by shock and vibration created on the normal operation of the circuit breaker. When the circuit breaker is manually opened from its closed position to its off position, tremendous internal forces are released causing shock and vibration that is transmitted to the flux transfer magnetic trip actuator. This shock and vibration has a tendency to release the armature of the flux transfer magnetic trip actuator sending the circuit breaker into its trip position. This can cause problems when the circuit breaker is being monitored by other electrical apparatus that receives a signal from the circuit breaker when it is in its trip position. Thus, a problem is created when it is desired to manually turn off the circuit breaker but due to shock and vibration, the circuit breaker may go into its tripped state and therefore give false indications of overload conditions that may not exist.